1. Field of the Invention
This invention relates to a tensioner for an endless power transmission belt.
2. Prior Art Statement
In the art of transmitting power employing an endless polymeric power transmission belt, such as driving or rotating driven sheaves of a plurality of automobile accessories using a belt which is driven by a driving sheave connected to the automobile engine crankshaft, it is difficult to maintain such belt under the tension required to assure non-slipping engagement and driving of the driven sheaves; and, numerous belt tensioners have been proposed and used heretofore in an effort to provide the required tension. Especially where one of the accessories being driven is the compressor of an air conditioning system for the automobile, such compressor upon being driven creates a tight side and a slack side in the belt on opposite sides of the compressor sheave. The tight side has a varying tightness of a cyclic character as a function of the inherent cyclic change in the load imposed by the compressor. It is a problem to provide the required tension in the overall belt as well as prevent any tendency of the belt to oscillate in an undesirable manner as a result of this cyclic load change. Further, many tensioners employed heretofore had a tendency to oscillate together with the belt.
It is known in the art to provide a tensioner for a power transmission belt which is adapted to be operated in an endless path and with the tensioner comprising a rotatable idler pulley, a supporting assembly for rotatably supporting and urging the pulley against the belt with a particular belt tensioning force with the assembly supported adjacent the belt, and a system for holding the assembly with the pulley urged against the belt.
Examples of tensioners of the character mentioned are presented in the following items:
(1) U.S. Pat. No. 3,413,866 PA1 (2) U.S. Pat. No. 4,108,013 PA1 (3) U.S. Pat. No. 4,249,425.
It appears from item (1) above that a holding system for a belt tensioner is provided which comprises either a friction surface or a toothed surface and a spring is used to continuously urge an idler pulley against a belt in tensioning engagement resulting in a so-called "live" tensioner.
It appears from item (2) that a belt tensioner is provided wherein a wedge is employed and allows a lever arm which carries an idler pulley to move in one direction to maintain a constant tension on the belt while restricting movement of the lever arm in an opposite direction.
It appears from item (3) that a tensioning mechanism is provided which utilizes a vacuum motor to hold an idler pulley urged against a belt.
It is an object of this invention to provide an improved tensioner for an endless power transmission belt.
Another object of this invention is to provide a tensioner of the character mentioned which is controlled in part by the ambient temperature of the belt.
Another object of this invention is to provide an improved method of making a belt tensioner.
Other aspects, embodiments, objects, and advantages of this invention will become apparent from the following specification, claims, and drawings.